Process for the manufacture of metals or alloys poor in carbon and silicon



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SWEDEN, ASSIGNORS TO AKTIEBOLAGET FERROLEGERINGAR, OF STOCKHOLM, SWEDEN, A. LIMITED JOINT STOCK COMPANY.

PROCESS FOR THE MANUFACTURE OF METALS R ALLOYS P003, IN CARBON AND SILICON.

Ito Drawing.

provements in Processes for the Manufacture of Metals or Alloys Poor in Carbon and Silicon, of which the following is a specification.

This invention relates to the manufacture of metals or alloys having a low ercentage of carbon and silicon, the principal object of the invention being to provide a process whereby such metals or alloys can readily be manufactured in an electric furnace without the passage of carbon into the charge during the process.

The present invention is based upon the fact that silicon has the property of being able to expel carbon from a metal or alloy. Consequently, an alloy having a high percentage of silicon necessarily has a low percentage of carbon. Therefore, in order to as produce as a final product a metal or alloy poor in both carbon and silicon, it is necessary to start with an alloy rich in silicon, which alloy ma be produced in any desired manner. t is preferable that this so alloy contain at least 10 per cent of silicon,

since, if a smaller percentage be present, the content of carbon will not have decreased sufliciently to be regarded as low. If preferred, more or less pure silicon, for examv ple, in the form of high per cent ferro-silicon, may be employed. This alloy, rich in silicon, is then melted, together with substances containing oxides of metals which are capable of oxidizin silicon, such, for

instance, as the oxides o chrome, vanadium,

manganese, tungsten, iron, nickel, and the like, and if necessary a sultable flux, such for instance as lim;-, magnesia, or the like,

maiy be added to the molten mass. as f the process can be carried on under such condltions as to obviate the absorption of carbon by the charged raw material or by the products formed, the metal or alloy produced will obviously not contain, absoso lutely speaking, a larger quantity of carbon than that charged with the raw material, and is thus, poor in carbon and silicon, pro- Application filed February 1, 1922. Serial No. 533,381.

vided the oxidation of the silicon has been carried sufiiciently far.

As a general rule, in order to get the oxidation of the silicon started, it is necessary that the heating should take place at such a high temperature that the electric furnace is the only suitable apparatus for the purpose. The furnace, however, must be so constructed that it works with a free electric arc, that is, so that its electrodes do not come into contact with the charge, as otherwise the carbon from the electrodes will be absorbed by the charge, and this is especially true in the treatment of substances which contain one or more of the oxides of chrome, vanadium, manganese, or tungsten.

It is, however, known that in such electric furnaces the energy supplied is badly utilized, and moreover, that the part or parts of the lining which are directly exposed to the radiation from the electric are are rapidly consumed, both of which ci'r: cumstances entail comparatively poor economic results. It is also known that the two drawbacks just mentioned inthe electric furnace working with a free electric are are considerably lessened in that type of electric furnace where the electric current, wholly or partially, must passfrom one or more movable electrodes directly to the charge.

To be able to use an electric furnace of.

the latter type for the process in question is therefore a desideratum, the realization of which has hitherto been frustrated by the fact that the charge absorbs carbon from the electrode or electrodes. The inventors of the present invention have, however, discovered that an electric furnace of the type above referred to can be used for the abovementioned process of manufacturing metals or alloys poor in carbon or silicon-without low 70 volts during the process.

The inventors have, moreover, ascertained B0 MICHAEL STURE KALLING AND SVEN DAGOBERT D ANIELI, OF TROLLHATTAN,

that the kind of s stem adoptedwhether single-phase or po yphase alternating current, or direct currentdoes not affect the result.

In order that the reaction between the silicon of the charged alloy rich in silicon, on

the one hand, and the oxides supplied for the oxidation of the silicon, on the other, may be carried sufficiently far, the oxides must be present in a certain excess. The inventors have, however, ascertained that this excess can be lessened in proportion to the fineness of grain of the reagents and the thoroughness of the mixture and that the minimum excess of oxidizing a ents may be used when the mixture of the Enely crushed materials is supplied to the furnace in the form of briquettes.

In the manufacture of the briquettes, any binding mediums employed must, of course, be practically free from carbon. Water glass, clay, cement, etc., have been found to be suitable binding media for this purpose. It is likewise advantageous that the briquettes, before use, should have been heated to such a high temperature that all traces of moisture have been expelled, for which pur pose the briquettes in general require to be heated to a temperature of over 500.

The above stated process for the manufacture of metals and alloys poor in carbon and silicon has, after thorough experiments, been used by the inventors with success for the manufacture of chrome manganese, vanadium, and tungsten, and for the manufacture of alloys of those substances with iron, nickel', or both.

In order further to make plain the invention, an example will be given of'the manufacture of ferro-manganese poor in carbon and silicon in accordance with the above stated process.

A silico-manganese alloy containing, for

example, 22 per cent of silicon, and less than- I 1 per cent of carbon, is ground to fine powder, and is thoroughly mixed with finely ground manganese ore, previously heated to redness and with ground, dead dolomite in suitable proportions. The mixture is briquetted with a solution of water-glass as a binding medium, whereupon the briquettes are dried and baked.

An electric furnace with a single adjustable electrode, and with alining which does not contain carbon, is supplied with electric power in the form of a single-phase alternatin current v. ".h such high voltagethat the e ective ohmic voltage drop between the point of the electrode, and the lining of the furnace will have a minimum value of volts. The electrode is brought suflicientl close to the furnace bottom to cause an electric arc to arise between the bottom and electrode. When the arc has been maintained for a sufiicient length of time to enable the ment when the resistance of the charge itself is put in circuit, care must be taken that the effective voltage drop between the point of the electrode and the charge is maintained above 70 volts, for which purpose it may be necessary to raise the voltage supplied to the furnace. When the first charge of briquettes has melted, the furnace is charged with a fresh quantity, and this procedure is continued until a suitable total quantity has been smelted, whereupon the content of the fur nace is tapped off, the furnace is charged with a fresh quantity of briquettes, and so forth. If the percentage of ore in the briquettes has been properly adjusted, the ferromanganese obtained will contain less than 1% of carbon and less than 2% of silicon. The slag simultaneously obtained will contain about 30% of Mn, and can suitably be used as raw material for the manufacture of silico-manganese. It will be understood, of course, that the expression process of manufacturing metals used in the claims is intended to cover not only manufacturing of metals as such, but also alloys of metals.

Having thus described our invention we declare that what we claim is:

1. The process of manufacturing metals poor in carbon and silicon, which consist-s in producing an alloy rich in silicon, mixing with said alloy an agent capable of oxidizing silicon, heating the mixture in an electric furnace, and maintaining the effective ohmic voltage-drop between the points of the electrodes of the furnace and the charge above 70 volts.

2. The process of manufacturing metals poor in carbon and silicon, which consists in producing an alloy rich in silicon, mixing with said alloy a flux and an agent capable of oxidizing silicon, heating the mixture in an electric furnace, and maintaining the effective ohmic voltage-drop between the points of the electrodes of the furnace and the charge above 70 volts.

3. The process of manufacturing metals poor in carbon and silicon, which consists in producing an alloy containing at least 10 per cent of silicon, mixing with said alloy an agent capable of oxidizing silicon, heating the mixture in an electric furnace, and maintaining the effective ohmic voltage-drop between the points of the electrodes of the furnace and the charge above 70 volts.

4. The process of manufacturing metals poor in carbon and silicon, which consists in producing an alloy rich in silicon, mixing with said alloy an oxide of a metal capable of oxidizing silicon, heating the mixture in an electric furnace, and maintaining the effective ohmic voltage-drop between the points of the electrodes of the furnace and the charge above 70 volts.

5. The process of manufacturing metals poor in carbon and silicon, which consists in producing an alloy containing at least 10 per cent of silicon, mixing with said alloy chromium oxide, heating the mixture in an electric furnace, and maintaining the effective ohmic voltage-drop between the points of the electrodes of the furnace and the charge above 7 0 volts.

6. The process of manufacturing metals poor in carbon and silicon, which consistsin producing an alloy rich in silicon, mixing with said alloy a flux and chromium oxide, heating the mixture in an electric furnace, and maintaining the effective ohmic voltagedrop between the points of the electrodes of the furnace and the charge above 7 0 volts.

7. The process of manufacturing metals poor in carbon and silicon, which consists in producing an alloy rich in silicon, mixing with said alloy an excess of an agent capable of oxidizing silicon, heating the mixture in an electric furnace, and maintaining the effective ohmic voltage-drop between the points of the electrodes of the furnace and the charge above 70 volts.

8. The process of manufacturing metals poor in carbon and silicon, which consists in producing an alloy rich in silicon, pulver-.

izing said alloy and mixing therewith a pulverized .agent capable of oxidizing silicon,

heating the mixture in an electric furnace,

and maintaining the ffective ohmic voltagedrop between the points of the electrodes of the furnace and the charge above 70 volts.

9. The process of manufacturing metals poor in carbon and silicon, which consists in producing an alloy rich in silicon, pulverizing said alloy and mixing therewith a pulverized agent capable of oxidizing silicon, binding said mixture together in the form of briquets, heating said briquets in an electric furnace, and maintaining the effective ohmic voltage-drop between the points of the electrodes of the furnace and the charge above 7 0 volts.

10. The process of manufacturing metals poor in carbon and silicon, which consists in producing an alloy rich in silicon, pulverizing said alloy and mixing therewith a pulverized agent capable of oxidizing silicon, adding to said mixture a binding material free from carbon, forming said mixture into briquets, heating said briquets in an electric furnace, and maintaining the effective ohmic voltage-drop between the points of the electrodes of the furnace and the charge above 70 volts. p

11. The process of manufacturing metals poor in carbon and silicon, which consists in producing an alloy rich in silicon, pulverizing said alloy and mixing therewith a pulverized agent capable of oxidizing silicon, adding to said mixture a solution of waterglass and forming the same into briquets, heating said briquets in an electric. furnace, and maintaining the effective ohmic voltagedrop between the points of the electrodes of the furnace and the charge above 7 0 volts.

12. The processof manufacturing metals poor in carbon and silicon, which consists in producing an alloy rich in silicon, pulverizing said alloy and mixing therewith a pulverized agent capable of oxidizing silicon, adding to said mixture a binding substance free from carbon, and forming said mixture into briquets, heating said briquets to a temerature of at least 500 (3., charging the riquets into an electric furnace, and maintaining the effective ohmic voltage-drop between the points of the electrodes of the fur- ,nace and the charge above 70 volts.

13. The process of manufacturing ferrochromium poor in carbon and silicon, which consists in producing an alloy of chromium rich in silicon, mixing with said alloy an excess of chromium ore, heating said mixture in an electric furnace, and" supplying current to the furnace at such a voltage that the effective ohmic voltage-drop between the points of the electrodes of the furnace and BO MICHAEL STURE KALLING. Y SVEN DAGOBERT DANIELI.

, Witnesses:

goo HAGEIIN, 

